Week 4: Special Senses

What are the 4 major types of receptors for your senses?

mechanoreceptors, chemoreceptors, photoreceptors, and thermoreceptors

accessory structures for the eye

eyelids- brush particles out of eye, cover eye

eyelashes- trap particles and keep them out of eye

ciliary glands- sweat glands between eyelashes to kill bacteria and lubricate eyelashes

lacrimal apparatus

lacrimal apparatus

• lacrimal gland- produces lacrimal fluid (tears)

• lacrimal canals- drains fluid from eyes

• lacrimal sac- passage of fluid towards nasal cavity

• nasolacrimal duct- empties lacrimal fluid into nasal cavity

three layers of the eye

the three layers are called

• fibrous tunic (outermost)

• vascular tunics (middle)

• retina (innermost)

Fibrous Tunic composition

composed of:

• sclera - protects and supports the eyeball (the white part of your eye)

• cornea - the transparent anterior portion of the fibrous tunic which refracts light as it enters the eye

Vascular tunic composition

composed of:

• choroid- blood rich layer containing a dark pigment which prevents light from scattering within the eye

• ciliary body- important to controlling lens shape through attachment to the lens by the supensory ligaments

  • composed of muscle

  • as the ciliary muscles contract, the lens shape changes to allow for focusing

• iris - composed of smooth muscle and reflexively contracts to regulate the amount of light that enters through the middle opening of the iris called the pupil

  • colored part of your eye

• pupil- an opening in your eye that decides the amount of light entered into the eye cavity

• lens- refracts light

Retina composition

• vitreous body (vitreous humor)- gel like substance that holds the retina in place

• optic disc (blind spot) - the site at which the optic nerve exits the eyeball, has no photoreceptors

• macula lutea- an area of high cone density (color photoreceptors)

• fovea centralis - a tiny pit that contains mostly cones and is the greatest in visual acuity

  • located in the center of the macula lutea

Photoreceptors

Rods- not as detailed/accurate but will activated more in the dark

• found toward edge of retina

• allow dim light vision and peripheral vision

• perception is all in gray tones

Cones

• allow for detailed color vision

• densest in center of retina

Describe the visual pathway

photoreceptors.. optic nerve.. crosses optic chiasma.. optic tracts.. thalamus.. visual cortex of occipital lobe

Areas of the ear

• outer (external ear)

• middle ear

• inner ear

External Ear

• pinna (auricle)- collects sound

• external auditory canal - channels sound inward

Middle Ear

• tympanic membrane - vibrates to transfer waves to the bones (eardrum)

• auditory tube- connects middle ear to throat

  • closing the tubes at a pressure changes, when they re-open = ears just popped

• three bones - sounds waves to inner ear

  • malleus

  • incus

  • stapes

Inner ear composition

• cochlea- convert sound to neural impulses

• vestibule- equilibrium (static)

• semicircular canals- balance (dynamic- movement happens on 3d planes)

olfaction (smell) structural composition

• olfactory receptors are in the roof of the nasal cavity

• olfactory epithelium- cilia lining the nasal cavity which help to move molecules and bind things to receptors

olfactory pathway

molecules enter the nasal passageway and bind to olfactory receptor.. olfactory bulb.. olfactory tract and either goes to

1. medial olfactory tract… hypothalamus.. septal nucleus of the limbic system

2. lateral olfactory tract… hippocampus.. caudate nucleus of basal ganglia

gustation (taste) structural composition

• taste buds- house receptor organs, found on sides of papillae

• papillae

  • filiform papillae- sharp, no taste buds, helps tongue move food

  • fungiform papillae- rounded, taste buds

  • circumvallate papillae- large with taste buds

  • foliate papillae- rounded, taste buds

how do we taste?

• tastants enter the taste pores on taste buds

• interact with microvilli on the surfaces of specialized taste cells

• brain interprets the taste as either sweet, salty, bitter, sour, or umami

gustatory pathway

before medulla:

• facial nerve (VII): taste buds (anterior 2/3) to medulla

• glossopharyngeal nerve (IX): taste buds (posterior 1/3) to medulla

• vagus nerve (X): posterior tongue and throat to medulla

After Medulla:

• medulla to thalamus to gustatory cortex in insula

General Senses of Touch

• temperature- thermoreceptors (heat)

• pressure- mechanoreceptors (movement)

• pain- mechanoreceptors

Special senses

• smell- chemoreceptors

• taste- chemoreceptors

• sight- photoreceptors (light)

• hearing- mechanoreceptors

• equilibrium- mechanoreceptors (balance)